The present invention relates to a press having a slide and a press bed for upper and lower parts of tools, a transfer device for the transport of sheet metal parts through the press, and a drawing apparatus with drawing cylinders fixed to the press frame which, during the shaping of the sheet metal parts, can be acted upon so that they can be lowered with the slide movement and, for the ejecting of the sheet metal parts from the bottom part of the tool, can be acted upon in a liftable manner and act from below on the tool-side sheet metal holder.
During the drawing in a press, the sheet metal part must be held against a contact pressure area in the top part of the tool by means of a sheet metal holder in the bottom part of the tool. After the drawing, the sheet metal part must be lifted up to the removal position for the transfer device. The blank-holding forces and the ejector forces or movements are applied by a drawing apparatus in the press bed below the bottom part of the tool. Up to now, the ejector movement had always taken place into a position which corresponded to the inserting position for the sheet part that follows. If the ejector movement carried out by the drawing apparatus had been interrupted temporarily, this took place for very different purposes.
In order to avoid a lifting of the pressure cheek that takes place at the same time as the upward movement of the press slide and thus an immediate lifting of the sheet metal part out of the bottom part of the tool, a locking cylinder is connected with the drawing apparatus in a device described in German Patent Document DE-PS 656 684.
From the German Patent Document DE-AS 24 08 096, it is known to let the piston rod of the drawing cylinder(s) and the piston rod of a locking cylinder act separately on the pressure cheek.
In the European Patent Document EP 0 276 672 A2, a drawing apparatus in a press is shown in which the locking arrangement can selectively be rendered operative or inoperative. In this case the drawing apparatus, as a whole, is rendered inoperative during certain machining stages.
Furthermore, it is known from German Patent Document DE 35 05 984 A1, in a drawing apparatus, to start the ejector movement of the sheet metal holder in a time-delayed manner following the upward movement of the slide. In this case, the speed of the ejector movement must be controlled into the receiving position which here also corresponds to the inserting position.
In German Patent Document DE 38 07 683 A1, the moving sequences, which are independent of the slide movement, such as the pre-accelerating and the ejecting, are to be controlled by means of a central unit in order to achieve a synchronizing of the pistons, which act in parallel, in the upward-moving stages, while they are mechanically independent of one another. Furthermore, by means of the central unit, the intermediate height adjustments of the sheet metal holder as well as its stroke starting position must be centrally presettable. For removal, the drawn sheet metal part is lifted into the inserting plane. For the temporary interruption of the ejector movement, the drawing cylinders interact with stopping cylinders during the ejection, the path of the stopping cylinders being controlled hydraulically.
A path-controlled stop for the temporary interruption of the ejector movement is also known from German Patent Document DE 40 32 338 A1. The drawing apparatus shown here acts upon a pressure cheek divided into segments. The drawing cylinders are fixedly arranged on the press. By way of forcing levers, the piston rods of the drawing cylinders act upon a liftable and lowerable console which, again by way of forcing levers, acts from below upon the segments of the pressure cheek. Locking cylinders are provided which are applied to the console by means of a lift bridge and, when acted upon by pressure, prevent an upward movement of the console and thus of the divided pressure cheek. The point in time of the stop in the upward-moving stage can be determined by a valve control of the pressure in the locking cylinders. The upward-carrying (ejector) movement of the pressure cheek is resumed at a point in time which is delayed with respect to the upward movement of the slide. In this case also, the sheet metal part is lifted into the upper position of the drawing apparatus which corresponds to the inserting position.
An object of the present invention is to remove the drawn sheet metal part from the sheet metal holder already in a stage of the upward movement of the drawing apparatus that is as early as possible in order to also utilize a long period of time of the upward movement of the slide for the transfer movement. For this purpose, the transfer device must be lowered further, and the movements of the transfer device and of the drawing apparatus and the point in time of the removal of the sheet metal part from the sheet metal holder must be controlled as a function of the slide movement, for example, as a function of the angle of rotation.
This and other objects are achieved by the present invention which provides a press having a press frame and at least one slide and a press bed for top and bottom parts of tools. The press bed has a tool-side sheet metal holder. The press also has a transfer device for transporting of sheet metal parts through the press, a drawing device with drawing cylinders which are fixed to the press frame and have piston rods which, during shaping of the sheet metal parts, can be acted upon so that the piston rods are lowerable with the slide movement and, for ejecting the sheet metal parts from the bottom part of the tool. The piston rods are liftable so as to act from below on the tool-side sheet metal holder. A liftable and lowerable console is provided through which the piston rods of the drawing cylinders act on the sheet metal holder. The console is operatively connected with at least one stop which is fixed to the press, and is removable in a controlled manner and has an adjustable stop position. The console, after passing through a lower dead center of the slide and the drawing device, is temporarily stopped as a function of a slide path or an angle of rotation in a removal position determinable by the stop.
Certain advantages result from the utilization of the upward moving stage of the slide for transfer movements. The number of strokes can be increased. Furthermore, larger transfer steps may take place. The lift-out movement by means of the drawing apparatus and the lifting movement of the sheet metal part by means of the transfer device can also be varied.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.